High efficiency hybrid PEDOT:PSS/nanostructured silicon Schottky junction solar cells by doping-free rear contact†
A high doping technique has been widely used for record-efficiency crystalline silicon (Si) solar cells to minimize the series resistance losses and to form a back surface field. However, it requires high temperatures (up to 1000 °C) and involves toxic gases, which may not be compatible for hybrid organic–silicon solar cells. Here, we report that a high power conversion efficiency (PCE) of 13.7% with a device area of 0.8 cm2 has been achieved for organic-nanostructured Si hybrid solar cells by inserting a cesium carbonate (Cs2CO3) layer between Si and the rear electrode aluminium (Al), which is realized by a solution process under low-temperature annealing (<150 °C). Transient and constant current–voltage, capacitance–voltage, and scanning Kelvin probe microscope measurements are used to characterize the effect of the Cs2CO3 layer on the device performance. The insertion of Cs2CO3 not only decreased the contact resistance, but also generated a built-in electric field on the rear electrode. The recombination rates are suppressed at the back surface due to the deflection of minority carriers. These findings show a promising strategy to achieve high performance organic–silicon solar cells with a simple, low temperature and cost effective process.