Side Connection for High-Efficiency Organic Photovoltaic Modules for Indoor Applications: Shunt Reduction and Performance Improvement

Indoor photovoltaics has attracted increasing attention because of its potential to power devices of the Internet of Things. The power conversion efficiency (PCE) of organic photovoltaic (OPV) cells has reached values beyond 30% under indoor light, but for OPV modules it is still significantly lower. One reason is the full width interconnection of subcells in such modules. Here, a new side connection method is presented which significantly reduces shunts and thus improves performance of OPV modules for indoor applications where a large parallel resistance is crucial. To prove its advantage, OPV modules are fabricated on both indium tin oxide (ITO) and ITO-free substrates. Under 500 lux cool white light emitting diode light, the highest PCE of ITO-free side connection modules (SCMs) is 15.1%, while for conventional full width connection modules (FWCMs) it is 14.4%. For ITO-based modules under 1000 lux, it is 2.3% for FWCMs compared to 12.1% for SCMs. Thermography images show that the improvement stems indeed from the reduction of shunts. Finally, results from experiments as well as from numerical simulations illustrate clearly that efficiency losses stemming from the increased series resistance for the side connection are rather small and that they are overcompensated by the increased shunt resistance.