Scientists at UNIST have developed high‐efficiency, solution‐processed, hybrid series, tandem photovoltaic devices featuring CQDs and organic bulk heterojunction (BHJ) photoactive materials. The retention of the organic back‐cell adequately remunerated the optical loss in the CQD front‐cell, which improved the overall photon harvesting.
Quantum dabs (QDs) are semiconductor particles with sizes smaller than a couple of nanometres. As they show fascinating phenomena, for example, size-dependent wavelength, the absorption spectra of the solar cell can be very alterable. The benefit of QDs is that it shows light absorption in the near-infrared (NIR) region, which other photoactive layers can’t. Be that as it may, there are a few ares in the NIR region where light ingestion doesn’t happen, even with QDs.
In work, analysts created high‐efficiency organic hybrid series tandem photovoltaic gadgets, highlighting CQDs and organic BHJs as photoactive materials to make up for the external quantum efficiency (EQE) misfortune in the NIR region. The NIR‐absorbing organic BHJ devices were utilized as the back sub‐cells to harvest the transmitted NIR photons from the CQD front sub‐cells.
Scientists also optimized the short‐circuit current density balance of each sub‐cell and thus created a near-ideal series connection using an intermediate layer to achieve a power conversion efficiency (PCE) that is superior to that of each single‐junction device. Indeed, the PCE (12.82% ) of the hybrid tandem device was the highest among the reported CQDPVs, including single‐junction devices and tandem devices.
As these hybrid tandem solar cells are created at room temperature using a solution process, the solar cells are affordable, more economical, and having less cost as compared to silicon solar cells. Their lower manufacturing costs also gives them a clear advantage of mass production.
Professor Sung-Yeon Jang in the School of Energy and Chemical Engineering at UNIST, said, “The hybrid tandem device exhibited almost negligible degradation after air storage for three months. Moreover, this study suggested the potential to achieve PCE > 15% in hybrid tandem devices by reduction of energy loss in CQDPVs and enhancement of NIR absorption in OPVs.”
The findings of this research have been published in the prestigious journal, Advanced Energy Materials on January 13, 2020.