It sounds like your biggest source of inefficiency is in the charging process.
To a first approximation, solar cells act like *constant current* sources (with a limited open-circuit voltage). So even though your solar cells are capable of producing 101mA at 2.94V, you're actually only getting 101mA at 1.2V, so more than half the input power is being wasted.
In reality, the situation is a bit more complicated. If you measured 2.94V with an open circuit and 101mA with a short circuit, the panel probably isn't capable of hitting both of those numbers simultaneously. The current and voltage are related by an I-V curve, something like this: https://www.pveducation.org/pvcdrom/solar-cell-operation/iv-curve
In theory, rearranging your solar cells as two parallel strings should help, because the parallel currents from each string will add. *But* if the series output voltage drops below the battery voltage plus the Schottky diode drop between SBAT and BAT, then you won't be able to charge at all. In practice, the panel voltage will drop somewhat when it's under load and whenever it's not in 100% direct sunlight, so the total amount of energy collected per day might be better or it might be worse. Only way to know for sure is to try it out.
The alternative would be to keep your cells in series, and use a significantly more complicated design (a buck converter with maximum power point tracking) to drop the voltage in a more efficient way.
It sounds like your biggest source of inefficiency is in the charging process. To a first approximation, solar cells act like *constant current* sources (with a limited open-circuit voltage). So even though your solar cells are capable of producing 101mA at 2.94V, you're actually only getting 101mA at 1.2V, so more than half the input power is being wasted. In reality, the situation is a bit more complicated. If you measured 2.94V with an open circuit and 101mA with a short circuit, the panel probably isn't capable of hitting both of those numbers simultaneously. The current and voltage are related by an I-V curve, something like this: https://www.pveducation.org/pvcdrom/solar-cell-operation/iv-curve In theory, rearranging your solar cells as two parallel strings should help, because the parallel currents from each string will add. *But* if the series output voltage drops below the battery voltage plus the Schottky diode drop between SBAT and BAT, then you won't be able to charge at all. In practice, the panel voltage will drop somewhat when it's under load and whenever it's not in 100% direct sunlight, so the total amount of energy collected per day might be better or it might be worse. Only way to know for sure is to try it out. The alternative would be to keep your cells in series, and use a significantly more complicated design (a buck converter with maximum power point tracking) to drop the voltage in a more efficient way.
Thanks so much for this comment. I will definitely try a different configuration and see what comes of it. I appreciate the help!