High Efficiency (>17%) Si-Organic Hybrid Solar Cells by Simultaneous Structural, Electrical, and Interfacial Engineering via Low-Temperature Processes

Highly efficient organic-inorganic hybrid solar cells of Si-poly(3,4-ethylenedi oxythiophene):polystyrene sulfonate (PEDOT:PSS) have been demonstrated by simultaneous structural, electrical, and interfacial engineering with low processing temperature. Si substrate has been sculpted into hierarchical structure to reduce light reflection loss and increase interfacial junction area at the same time. Regarding the electrical optimization, highly conductive organic PEDOT: PSS layer has been formulated with low sheet resistance. It is argued that the sheet resistance, rather than conductivity, is the primary parameter for the high efficiency hybrid cells, which leads to the optimization of thickness, i.e., thick enough to have low sheet resistance but transparent enough to pass the incident sunlight. Finally, siloxane oligomers have been inserted into top/bottom interfaces by contact-printing at room ambient, which suppresses carrier recombination at interfaces and reduces contact resistance at bottom electrode. Contrary to high-temperature doping (for the formation of front surface or back surface fields), wet solution processes or vacuum-based deposition, the contact-printing can be done at room ambient to reduce carrier recombination at the interfaces. The high efficiency obtained with low processing temperature can make this type of cells be a possible candidate for post-Si photovoltaics.