Jingyu Zou

Air-stable inverted flexible polymer solar cells using zinc oxide nanoparticles as an electron selective layer

The performance and stability of unencapsulated inverted bulk-heterojunction solar cells with zinc oxide (ZnO) made by different processes as the electron selective contact are compared to conventional bulk-heterojunction solar cells. The low temperature processed inverted devices using ZnO nanoparticles on indium tin oxide plastic substrates showed high power conversion efficiency of ∼3.3%. This inverted device structure possessed much better stability under ambient conditions retaining over 80% of its original conversion efficiency after 40days while the conventional one showed negligible photovoltaic activity after 4days. This is due to the improved stability at the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/Ag interface.

Metal grid/conducting polymer hybrid transparent electrode for inverted polymer solar cells

A simple method was developed using metal grid/conducting polymer hybrid transparent electrode to replace indium tin oxide (ITO) for the fabrication of inverted structure polymer solar cells. The performance of the devices could be tuned easily by varying the width and separation of the metal grids. By combining the appropriate metal grid geometry with a thin conductive polymer layer, substrates with comparable transparency and sheet resistance to those of ITO could be achieved. Polymer solar cells fabricated using this hybrid electrode show efficiencies as high as ∼3.2%. This method provides a feasible way for fabricating low-cost, large-area organic solar cells.

Conjugated polymers based on C, Si and N-bridged dithiophene and thienopyrroledione units: synthesis, field-effect transistors and bulk heterojunction polymer solar cells

A series of low band-gap conjugated polymers (PDTC, PDTSi and PDTP) containing electron-rich C-, Si-, and N-bridged bithiophene and electron-deficient thienopyrroledione units were synthesized viaStille coupling polymerization. All these polymers possess a low-lying energy level for the highest occupied molecular orbital (HOMO) (as low as −5.44 eV). As a result, photovoltaic devices derived from these polymers show high open circuit voltage (Voc as high as 0.91 V). These rigid polymers also possess respectable hole mobilities of 1.50 × 10−3, 6.0 × 10−4, and 3.9 × 10−4 cm2 V−1s−1 for PDTC, PDTSi, and PDTP, respectively. The combined high Voc and good hole mobility enable bulk hetero-junction photovoltaic cells to be fabricated with relatively high power conversion efficiency (PCE as high as 3.74% for the PDTC-based device).

Interfacial engineering of ultrathin metal film transparent electrode for flexible organic photovoltaic cells.

and good fi lm quality in order to get optimal transparency and low sheet resistance. The continuity of ultrathin Ag fi lm is governed by its nuclea-tion and growth kinetics on substrate, which can be affected by the surface energy of the seed layer and the deposition condi-tions. The poor wettability of Ag on electrically insulating sub-strates (i.e., glass, polyethylene naphthalate (PEN)) often leads to poor fi lm continuity due to unfavorable disparity in surface energy and poor adhesion to the substrate.

Solution processed inverted tandem polymer solar cells with self-assembled monolayer modified interfacial layers

Inverted tandem bulk-heterojunction solar cells with comparable efficiency to single layer devices have been demonstrated by utilizing two thin layers (∼50 nm) of poly-(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester as the active material and a fullerene self-assembled monolayer (C60-SAM) to modify the interfaces between the ZnO buffer layer and the active layer. Single and tandem solar cells without the SAM modification have much lower efficiencies than the ones with modification. The successful demonstrations of inverted tandem devices with SAM modification give promise of further device improvements if active materials with complementary absorption can be used.

Evaluation of structure–property relationships of solution-processible fullerene acceptors and their n-channel field-effect transistor performance

A series of fullerene acceptors have been selected for the systematic study of their electron-transporting properties on a standardized field-effect transistor (FET) platform. It was found that small structural alternations, functional patterns, and number of addends on fullerene derivatives strongly affect their mobilities. The measured charge mobilities correlate well with structural features of these materials and provide useful insights into designing better fullerene-based semiconductors for organic electronics.