Solution processed photovoltaic devices with 2% infrared monochromatic power conversion efficiency: Performance optimization and oxide formation

Solution processed photovoltaic devices with 2% infrared monochromatic power conversion efficiency were optimized for a better understanding of material changes that contribute to the performance improvements. A series of devices were fabricated consisting of a porous ITO electrode with butylamine ligand-exhange solution-synthesized PbS nanocrystals. The vacuum annealed devices show a trend of increasing external quantum efficiencies (EQE) with increasing temperature, while maximum power conversion efficiency under monochromatic illumination is 0.08%. Aged devices are found to retain the bulk of their performance, diminishing approximately 20% in power conversion efficiency compared to fresh devices. The results also show that heating in inert or air atmospheres allow an increase in EQE, while annealing alone is not sufficient to increase open circuit voltage.