In solar cell there are two types of quantum efficiency: a) External quantum efficiency which is nothing but IPCE, b) Internal quantum efficiency which is APCE. When someone quote quantum efficiency then s/he should make clear whether it is EQE or IQE. Hope this helps.

IPCE is the same as QE, But  I think APCE refers to internal quantum efficiency only

Dear Tola

The Internal Efficiency (with respect to absorbed photons) is affected by internal resistance, series resistance, recombination, back contact quality and surface states.

External efficiency accounts to other additional factor, namely reflection and external loss of photons.

For practical purposes, we consider overall efficiency (observed efficiency) which is measured and accounts for all factors.

However, if you know incident light intensity, reflected light intensity, and you know measured reflectance, and you know observed efficiency, then you can find out internal efficiency (will be higher than measured efficiency)

Good luck

Thanks for your contributions. I take measurement regularly with this newport Instrument but it just shows up as QE, so I wanted to be sure it was IPCE I was doing and not APCE

Quantum efficeincy QE refers to external quantum efficiency EQE which is the ratio of the collected photo electron hole pair per incident photons in a specific wavelength.

The internal quantum efficeincy IQE is the same ratio except for absorbed photons only.

Please refer to the link: https://www.pveducation.org/pvcdrom/solar-cell-operation/quantum-efficiency

Best wishes

Does QE also depend on crystal structure of absorbing layer ?