Electro-Optics of Colloidal Quantum Dot Solids for Thin-Film Solar Cells

The electro‐optics of thin‐film stacks within photovoltaic devices plays a critical role for the exciton and charge generation and therefore the photovoltaic performance. The complex refractive indexes of each layer in heterojunction colloidal quantum dot (CQD) solar cells are measured and the optical electric field is simulated using the transfer matrix formalism. The exciton generation rate and the photocurrent density as a function of the quantum dot solid thickness are calculated and the results from the simulations are found to agree well with the experimentally determined results. It can therefore be concluded that a quantum dot solid may be modeled with this approach, which is of general interest for this type of materials. Optimization of the CQD solar cell is performed by using the optical simulations and a maximum solar energy conversion efficiency of 6.5% is reached for a CQD solid thickness of 300 nm. The experimental characterization and modeling of the internal optoelectric behavior and exciton generation rate in the quantum dot solids of the heterojunction PbS colloidal quantum dot solar cell is demonstrated. The proposed model shows good agreement with the experimental results, and the fabricated quantum dot solar cell shows a power conversion efficiency of 6.5%.