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Abstract title Parallel Tandem Solar Cell based on Highly Transparent Singlet Fission Organic Solar Cell
Author Dr. Lee, Jumin, AMOLF, Amsterdam, Netherlands (Presenting author)
Co-author(s) Pazos-Outón, Luis
Futscher, Moritz
Ehrler, Bruno
Abstract text

The single junction solar cell has a 34 % of power conversion efficiency limit, as we called Shockley–Queisser limit. Tandem configuration stacking of more than two junction system are theoretically allows to achieve maximum 45 % of efficiency by absorbing high and low energy photons together. Sub-cells in tandem configuration were mostly connected in series promoting the voltage of solar cell. However, efficiency of series tandem was difficult to maintain efficient photocurrent in solar spectrum changes. In this reason, we designed stable system in variable light spectrum introducing parallel-connected tandem configuration. The voltage-matching, requirements for parallel tandem was fulfilled by singlet fission (SF) pentacene solar cell together with commercial silicon (Si) solar cell. SF process in pentacene allows to convert one singlet exciton to two triplets resulting carrier multiplication. Our SF/Si tandem shows photocurrent addition from two sub-cells achieving higher than 100 % of external quantum efficiency owing to carrier multiplication. The efficiency limit of SF/Si tandem is decided by below-bandgap transparency of SF front cell. Therefore, we mainly focused on highly conductive and transparent metal layer as a top electrode. Multi-stacked thin metal layers prepared by vacuum evaporation facilitates higher than 80 % of solar cell transparency in below pentacene bandgap obtaining a half of photocurrent against opaque solar cell, helping to transfer most of low energy photons to the Si back-cell.