If the photovoltaic module is not coupled to an inverter or a load, it will remain in an open circuit (maximum voltage and zero current), meaning we have no electrical power.
solar panels can directly power certain DC devices without an inverter. If you would like to use DC devices (i.e. BLDC motor), you can use solar panels directly without having an inverter.
The time it takes for solar panels to start generating electricity is immediate upon exposure to sunlight, but the amount produced over time (of course, depends on factors like sunlight intensity and weather conditions).