Samenvatting
Our previously reported 17.8 % efficiency InP nanowire solar cell1 showed a short-circuit current Isc of 29.3 mA/cm2, which is not far from the theoretical maximum Isc = 34.6 mA/cm2, but the loss in the open circuit voltage with respect to the radiative limit still amounted to 272 mV. To avoid this loss and reach the radiative limit we have to increase both the internal radiative efficiency ηPlint and the photon escape probability Pesc towards unity, as shown by the last term in Eq. 1. 'Equation Presented' We report top-down etched InP nanowires intended to both optimize the amount of light outcoupling as well as the directionality of the emitted light. The photon entropy loss is governed by the ln ϵin/ϵout term, which is responsible for a 300 mV loss in the open circuit voltage. To circumvent this loss, we need to redirect all the emitted photoluminescence from the cell back to the sun (ϵin = ϵout), For this purpose, we have fabricated PMMA microlenses by using a reflow process, which can be precisely positioned with respect to the InP nanowires.
| Originele taal-2 | Engels |
|---|---|
| Titel | Physics, Simulation, and Photonic Engineering of Photovoltaic Devices XI |
| Redacteuren | Alexandre Freundlich, Stephane Collin, Karin Hinzer |
| Uitgeverij | SPIE |
| Aantal pagina's | 4 |
| ISBN van elektronische versie | 9781510648630 |
| DOI's | |
| Status | Gepubliceerd - 2022 |
| Evenement | SPIE OPTO 2022 - Online/Virtual, San Francisco, Verenigde Staten van Amerika Duur: 22 jan. 2002 → 28 feb. 2002 |
Publicatie series
| Naam | Proceedings of SPIE |
|---|---|
| Volume | 11996 |
| ISSN van geprinte versie | 0277-786X |
| ISSN van elektronische versie | 1996-756X |
Congres
| Congres | SPIE OPTO 2022 |
|---|---|
| Land/Regio | Verenigde Staten van Amerika |
| Stad | San Francisco |
| Periode | 22/01/02 → 28/02/02 |
Financiering
We have shown that microlenses allow significantly better focusing of the emitted light as well as an enhanced radiative recombination from the nanowire arrays. The Voc and the Jsc were also improved4 by the use of the lens in particular with the wires that are located in the focal spot of the lenses. However, limitations are still provided by fabrication issues as BCB layer homogeneity, that presently prevents us to contact ITO with all nanowires present within one cell. In our present design, the contacting pads were damaged after only a few measurements as we need to push through the BCB layer with our contacting tip. Nevertheless, our results are very promising to improve the solar cell performance by using lenses. The actual solar cell design presently consists out of an 500x500 μm array of nanowires with a top diameter of 180nm, a bottom one of 300nm and a center to center pitch of 500nm. A new design can easily be fabricated, where nanowires (3x3 array or even single wire) will be positioned below each microlens to reduce the entropy losses. This will allow us to reach better solar cell performance and demonstrate that the entropy losses can be reduced with a better outcoupling of the light. This work was supported by the Dutch Organization for Scientific Research NWO.