Luminescence Analysis of Charge-Carrier Separation and Internal Series-Resistance Losses in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mi>Cu</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:mi>In</mml:mi><mml:mo>,</mml:mo><mml:mi>Ga</mml:mi><mml:mo stretchy="false">)</mml:mo><mml:msub><mml:mi>Se</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math> Solar Cells

Abstract

This study investigates the phenomenon of $r\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}d\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l$ $l\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}e$ from an illuminated solar cell under low or zero voltage bias---a luminescence that shouldn't be there, in an ideal solar cell. More broadly, the investigation shows that residual luminescence is a generic consequence of the finite coupling strength between the electron-hole system inside the photovoltaic absorber and the external electrical circuit. For the important case of a classic $p\ensuremath{-}n$ junction, the authors derive an analytical expression for this coupling strength, and for experiments with a real Cu(In,Ga)Se${}_{2}$ solar cell, they offer an in-depth analysis of the efficiency losses resulting from the finite coupling. The conclusions of this work apply to $a\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}y$ solar cell.

Topics & Concepts