Photovoltaic effect in the single-junction DBP/PTCBI organic system under low intensity of monochromatic light

Photoelectric properties of the planar ITO/MoO3/DBP/PTCBI/BCP/Ag system were characterized on the basis of short-circuit current, open-circuit voltage and absorption spectra, and current-voltage measurements in the dark and under monochromatic illumination of low intensity. Photovoltaic performance of the system was compared with the performance of ideal semiconductor and excitonic cells of chosen bandgaps. Such analysis shows, that the fabricated cell exhibits quite high value of the open-circuit voltage, in comparison to the SQ limits calculated for semiconductor devices of bandgaps close to the LUMOPTCBI-HOMODBP offset or crystalline silicon cells of the same absorptivity. This confirms that the DBP/PTCBI junction exhibits good properties for conversion of exciton energy to chemical energy of electron-hole pair. Moreover, open-circuit voltage and short-circuit current of the investigated cell practically do not change within the 520 nm–620 nm range, for which they reach the maximum values, making the junction of DBP/PTCBI attractive for use in indoor photovoltaics.

Electric transport in organic system with planar DBP/F16ZnPc junction on the basis of direct current and small signal admittance spectra analysis

The objective of this work was to determine electric transport in the organic device based on a planar junction of electron donor and electron acceptor materials, namely ITO/MoO3/DBP/F16ZnPc/BCP/Ag. The analysis reported herein was based on direct current-voltage measurements and small-signal admittance spectra in the dark and under illumination. Such analysis may provide information on potential barriers, parasitic resistances and presence of space charge affecting the electric current flow within the device. Therefore, this approach could be applied for determination of physical processes related to electric charge transport within multilayer structures, such as photovoltaic cells or photodetectors. In the case of the investigated system, the parallel parasitic resistance, the resistance of electrodes, and the geometric capacitance of 10 MΩ, 55 Ω, and 1.6 nF respectively were found. It was also shown that the direct current flowing from ITO to Ag was limited by charge carrier injection from electrodes, while in the case of current flowing from Ag to ITO no essential barriers at electrodes were noticed.

Photovoltaic phenomena in devices with perfluorozincphthalocyanine layer

J. Szostak – 2016
The course of photovoltaic phenomenon in organic photovoltaic cells utilizing thin layers of perfluorozincphthalocyanine was studied in few single and planar bilayer configurations. Mechanisms of photogeneration and recombination of free charge carriers were determined and active interfaces were localized. In case of single layer cells these interfaces were located at the front electrode/F16ZnPc junctions, whereas photogeneration of free charge carriers in all investigated bilayer systems took place at the donor/acceptor junctions. Theoretical models describing the current-voltage behavior of single layer excitonic cells and planar bilayer cells (termed the CFA models) were developed. These models show how free charge carrier mobilities, electrode work functions, dielectric constants and thickness of donor and acceptor layers along with mono and bimolecular recombination constants affect the shape of the current-voltage curves. Knowing this dependence, such important physical quantities as the open-circuit voltage and short-circuit current were correlated with the aforementioned parameters. Subsequently, experimental data collected for all investigated systems were analyzed on the basis of the developed models and the Shockley equivalent circuit model commonly used for organic solar cells. Comparison of the derived CFA models and the SEC model brought some insight on the relation between physical properties of the layers forming the modeled cells and parameters characterizing performance of a cell, such as series and shunt resistances, diode ideality factor or photogeneration and saturation currents. Inter alia, it was possible to explain the illumination dependence of the shunt resistance commonly observed in case of organic solar cells. Moreover, it was shown that one of the layers of the D/A systems may govern the current flow and that the free charge carrier mobility is not necessarily the most important factor influencing the free charge carrier transport through the cell. Surprisingly, the best photovoltaic performance was shown by the single layer CuI/F16ZnPc/BCP/Ag cell. Further increase of the performance of this system is possible if optimization of the phthalocyanine layer is made. Relatively high values of fill factors and open-circuit voltage obtained in the course of this study lead to the conclusion, that F16ZnPc may be a promising material for the applications in the field of organic photovoltaics.

Photovoltaic properties of cadmium selenide–titanyl phthalocyanine planar heterojunction devices

Photovoltaic phenomenon taking place in cadmium selenide (CdSe)/titanyl phthalocyanine (TiOPc) planar heterojunction devices is described. Mechanisms of free charge carrier generation and their recombination in the dark and under illumination are analyzed, chosen photovoltaic parameters are presented.

Jedno- i dwuwarstwowe organiczne ogniwa fotowoltaiczne

Omówiona została zasada działania organicznych ogniw fotowoltaicznych na przykładzie ogniw jedno- i dwuwarstwowych. Przedstawione zostały procesy prowadzące do fotogeneracji swobodnych nośników ładunku w układach organicznych, ze szczególnym uwzględnieniem procesu dyfuzji oraz dysocjacji ekscytonu na złączu dwóch materiałów. Przytoczone zostały podstawowe wyrażenia na wartość napięcia fotowoltaicznego dla układów jedno- i dwuwarstwowych oraz wybrane napięcia

Struktury fotowoltaiczne z planarnym heterozłączem półprzewodnik II-VI / półprzewodnik molekularny

Artykuł przedstawia wybrane wyniki badań własnych nad układami hybrydowymi zbudowanymi na bazie złącza półprzewodnik nieorganiczny II-VI/półprzewodnik organiczny. Na podstawie analizy położenia pasm energetycznych warstw wchodzących w skład wytworzonych ogniw oraz charakterystyk spektralnych prądu zwarcia tych urządzeń określone zostały procesy prowadzące do fotogeneracji nośników ładunku w badanych układach. W ogniwach zbudowanych na bazie złącz CdS/ZnPc oraz ZnTe/F16ZnPc zaobserwowano zarówno generację bezpośrednią w półprzewodniku nieorganicznym (przejście pasmo-pasmo) jak i generację wynikającą z dysocjacji ekscytonów wzbudzonych w półprzewodniku molekularnym zachodzącą na złączu obydwu półprzewodników. W przypadku układów zbudowanych na bazie złącza CdTe/DIP zaobserwowano jedynie fotogenerację drugiego typu.

Photoelectric properties of a novel MEH-PPV/F16ZnPc heterojunction

Photoelectric properties of a novel poly[2-methoxy-5-(2-ethylhexyloxy-p-phenylenevinylen)] (MEH-PPV)/perfluorozincphthalocyanine (F16ZnPc) planar heterojunction provided with BCP and MoO3 buffer layers sandwiched between indium tin oxide (ITO) and Ag are shown. Efficient photogeneration of charge carriers at this junction is observed. Effect of bathocuproine (BCP) and MoO3 buffer layers on the performance of cells is analysed. Mechanisms of injection, generation, trapping and recombination of charge carriers in the dark as well as under illumination are discussed. Reliable exciton diffusion length in the F16ZnPc of (187) nm is evaluated.

Organic photovoltaics - chosen aspects

There are many types of organic and organic/inorganic (hybrid) photovoltaic devices that possess many beneficial properties over inorganic solar cells. That makes the former suitable for a broad range of applications and hence so much attention is paid to their development. In spite of intensive research carried on this field of science and technology there are still many crucial problems that need to be solved. Extensive knowledge on physical basis of operation of organic and hybrid systems, fast development of nanotechnology, great variety of organic materials and methods of their modification will pave the way for commercial applications of these devices.

Własności fotowoltaiczne układów organicznych

Praca omawia fizyczne podstawy zjawiska fotowoltaicznego w układach organicznych oraz badania tego zjawiska prowadzone na Wydziale Fizyki Technicznej i Matematyki Stosowanej Politechniki Gdańskiej.

Heterozłącze planarne polimer-materiał małocząsteczkowy

J. Szostak – 2010
Polimerowe ogniwa fotowoltaiczne ze względu na szereg zalet cieszą się dużym zainteresowaniem. Praca ta zawiera krótki opis zasady działania tego typu urządzeń oraz podstawowych zjawisk zachodzących we wnętrzu materiałów organicznych i na ich złączach. Przedstawiona została struktura heterozłącza planarnego i objętościowego oraz ich porównanie, z uwagi na fakt, że są to dwa najczęściej stosowane w ogniwach fotowoltaicznych typy heterozłączy. Artykuł przedstawia także strukturę badanych ogniw, materiały wchodzące w ich skład, metodę wytwarzania poszczególnych warstw oraz wybrane własności fotoelektryczne analizowanych urządzeń.