Photodiode showing triangle waves instead of square? (re: need op amp?)
The problem is in the parasitic capacitance of the circuit you have implemented. It forms an RC timeconstant with the gain resistor which filters out high frequency signals. There are plenty of resources to help you with this problem

You will need to minimize the capacitance and possibly get a faster opamp with more gain bandwidth product (GBWP). Breadboards are terrible for implementing circuits like this, even on a PCB traces can have enough capacitance (pFs) to make a difference, so short trace sizes are best between sensor and transimpedance amplifier.