Spectrum‐Driven AM0 Calibration of Space Solar Cells Using Near‐Space In Situ Measurements

Accurate calibration under the Air Mass Zero (AM0) spectrum is a prerequisite for interpreting the performance of space solar cells. Conventional AM0 calibration strategies implicitly treat AM0 as an environmental condition that can be approximated by operating at a specific altitude or by reproducing a target spectrum in laboratory simulators. In this work, AM0 calibration is formulated as a device‐dependent, spectrum‐driven problem rather than an altitude‐defined condition. The broadband solar spectrum (250–2500 nm) is synchronously measured during a near‐space balloon flight and combined with a calibrated spectral responsivity function to reconstruct the AM0‐equivalent short‐circuit current directly from measured spectral deviations, without using altitude alone as a proxy for AM0. Altitude‐resolved measurements reveal wavelength‐dependent atmospheric effects that persist into the lower stratosphere but influence photovoltaic output only within the device responsivity band. Consequently, spectral deviations outside the active wavelength range do not affect the reconstructed current. A crystalline silicon device is used as a case study to demonstrate that near‐space measurements acquired under varying spectral conditions can be reconciled into a consistent AM0‐equivalent response. These results demonstrate a spectrum‐driven route for AM0‐equivalent photovoltaic reconstruction from near‐space measurements, with potential extension to tandem and multijunction devices given calibrated spectral responsivity data.