In hybrid polymer photovoltaics, conjugated polymers are combined with wide bandgap metal oxide semiconductors like TiO2 or ZnO. Reported max. power conversion efficiencies (PCE) at AM1.5G conditions for a hybrid polymer bulkheterojunction device are up to 1.6 %. In this paper we report on the current-voltage characteristics of bi-layer devices consisting of TiO2 and a conjugated polymer. Several polymers with different optical bandgap were studied. The max. External Quantum Efficiency (EQE) of the devices is comparable, but the PCE differs considerably (0.2-0.5%). The differences can for a large part be explained by the differences in optical bandgap of the polymers. It is shown that a low band gap is beneficial for the short circuit current, but does not automatically result in a high PCE as relative shifts of the HOMO (HOMO) energy levels of the polymers reduce the open circuit voltage (Voc). The calcns. show that a PCE up to 19 % can be achieved using the max. possible Voc and a fill factor of 80%. Judicious engineering of material combinations is required to achieve such a power output, and it expresses the need for a continuing search on potentially low cost, efficient metal oxide/polymer BHJ structures.
|Name||Proceedings of SPIE|
|Conference||conference; Organic photovoltaics VI : 2 - 4 August, San Diego, California, USA; 2005-08-02; 2005-08-04|
|Period||2/08/05 → 4/08/05|
|Other||Organic photovoltaics VI : 2 - 4 August, San Diego, California, USA|